Synthetic plastics or rubbers are usually moulded under pressure. In transfer moulding a first large hydraulic cylinder usually closes the die or mould to hold the joint line tight against splash and then the charge is forced into the cavity by means of a smaller hydraulic cylinder. Injection moulding makes this process automatic by adding a hopper to maintain a supply of mouldable material, a control injection and a meter to feed the correct amount of mouldable material, a control heating zone to bring the charge up to temperature before it is injected into the mould cavities, a moulded article ejecting means and automatic cycle timing.
The injection moulding process is often used to mould or bond a plastics material (or any other material suitable for injection moulding) onto another article and this sometimes is referred to as insert injection moulding. The referred to another article is the insert which must be loaded into the split open mould before being closed. The insert is retained in the mould cavity and the mould closed following which the material is injected into the mould. The mould is then opened and the moulded article unloaded.
Loading an insert into a mould half and unloading an injection moulded composite article from the other mould half is known from the teachings of U.S. Pat. No. 4,368,018 issued Jan. 11, 1983 naming Herbert Reese and Klaus B. Fritzsche as inventors. This patent discloses a movable transport unit controlled by particular mechanical apparatus to deliver a single insert into one mould half and the patentees have indicated this loading can be done while "concurrently extracting a moulded workpiece from the other opposite mould portion". Movement of the transport unit is synchronized with movement of the mould half to an open and closed mould position. Accuracy and precision is not one of the patentees' concerns nor is the simultaneous moulding of multiple pieces nor is there any suggestion for checking the insert for accuracy before being loaded.
A process and device for controlling the movements of an injection mould and a handling device are disclosed in International PCT/DE/9100221 published August 1991 under WO91/11314 (Canadian National Phase Application Serial No. 2,074,940).
Insert injection moulding is also disclosed in Canadian Patent 923,268 issued Mar. 27, 1973 to E.S.B. Incorporated naming Ronald L. Daggett as inventor. This patent discloses utilizing magnets (permanent or electromagnets) to hold the insert in position in the mould and also a locator that engages and positions the insert.
None of the foregoing references disclose the problems associated with high output production while at the same time accomplishing precision insert moulding.